The invention relates to medical devices and methods for the infusion of fluids such as blood, blood products, and medications into a patient requiring circulatory volume replacement, with a capability for infusion over a range from slow to extremely rapid flow rates.
A variety of clinical circumstances, including massive trauma, major surgical procedures, massive burns, and certain disease states such as pancreatitis and diabetic ketoacidosis can produce profound circulatory volume depletion, either from actual blood loss or from internal fluid imbalance. In these clinical settings, it is frequently necessary to infuse blood or other fluids rapidly into a patient to avert serious consequences.
In the past, the replacement of large amounts of fluids has been a major problem to the medical or surgical teams attending a patient with these acute needs. A common method of rapid infusion involves the simultaneous use of a plurality of infusion sites. Frequently, a plurality of medical personnel are required to establish and oversee the various infusion sites and to personally ensure the flow of fluids from their respective container bags. This method may be limited by the number of peripheral or central sites that can be physically accessed in a given patient, the number of people attending the fluids being infused, as well as the efficiency of infusing the fluids during a dire, hypovolemic event. It is not uncommon for four to five anesthesiologists or technicians to stand in attendance during transplant operations lasting more than twenty-four hours attempting to infuse massive quantities of blood through five or six venous catheters.
Patients who have undergone massive trauma or surgery such as liver transplantations or other elective procedures may require voluminous quantities of fluids to maintain a viable circulatory state. Although it is not uncommon for an anesthesiologist or surgeon in a major trauma and transplantation center to encounter massive exsanguination of ten liters or more, it is unusual to successfully resuscitate a patient with such massive blood volume loss using traditional methods.
While the potential need for rapid infusion is present in a number of common clinical situations, the actual need is unpredictable and may arise suddenly during the course of treatment or surgery. Therefore, it would be advantageous to have a system that could rapidly transition from normal infusion to rapid infusion with minimal operational intervention.
In patients suffering blood loss, measuring the pressure in the large central veins (central venous pressure or C.V.P.), is a good objective method for assessing the efficacy of volume replacement. A low C.V.P. indicates that the patient does not have adequate intravascular volume and thus further fluid resuscitation is necessary. A high C.V.P. is an indication of volume overload and can result in heart failure and pulmonary edema (or fluid) in the lungs. Presently, C.V.P. is most commonly measured by placement of a large catheter in the patient""s neck that is connected to a pressure transducer. This transducer converts pressure changes into an electrical signal that is displayed on an oscilloscope-type monitor. Intensive care units and operating rooms are usually the only hospital areas capable of measuring C.V.P. In an emergency department setting, fluid administration is gauged empirically using mainly the patient""s blood pressure and pulse to assess the adequacy of volume replacement.
Rapid infusion devices are best used while monitoring C.V.P. The volume and rate of flow into the patient can then be quickly and accurately adjusted to sustain an adequate C.V.P., lessening the chances of complications of heart failure and pulmonary edema from fluid overload.
The prior art contains a number of devices and methods that have attempted to address the clinical need for rapid intravenous fluid infusion.
U.S. Pat. No. 5,840,068 to Cartledge discloses a device and method for the rapid delivery of an infusion of blood and/or volume expanding fluid to a patient. The device includes a pump system that interfaces with a fluid housing system.
U.S. Pat. No. 5,061,241 to Stephens, et al. discloses a rapid infusion device capable of high volume pumping. The device includes a permanent unit that includes a base portion that houses an AC/DC motor, a roller pump, and other associated gauges and switches. A disposable unit includes a fluid housing, heat exchange component, and associated tubing leading to the roller pump. The roller pump increases the volume of fluid being pumped by increasing the r.p.m. of the pumping unit and includes a pressure control valve.
U.S. Pat. No. 4,747,826 to Sassano discloses a portable infusion system consisting of supply sources, fluid housings, and associated tubes and valves leading to an infusion pump which can be a centrifugal or a roller head occlusive pump.
U.S. Pat. Nos. 4,187,057 and 4,537,561 to Xanthopoulos disclose peristaltic infusion pumps employing disposable cassettes to house the infused fluid. In the ""057 patent, the fluid conduit is held in the cassette in an arcuate configuration for its active interface with a pump rotor assembly. In the ""561 patent, the fluid conduit is held in the cassette in a linear configuration for its active interface with a pump rotor assembly. It appears that the pumps can provide only routine infusion rates.
U.S. Pat. No. 4,410,322, to Archibald discloses an intravenous infusion pump that employs a piston-cylinder pump and a disposable pump chamber. The pump chamber contains a linear series of diaphragm enclosures that propel the infused fluid from the action of the pump cycles. Dielectrical sensors are employed to detect the presence of air bubbles in the disposable pump chamber. When air is detected by the system, an alarm is sounded for operator intervention.
Intravenous infusion rates may be defined as either routine, generally up to 999 cubic centimeters per hour (cc/hr), or rapid, generally between about 999 cc/hr and 90,000 cc/hr (1.5 liters per minute) or higher. Most prior art infusion pumps are designed for medication delivery and are limited in their performance to the routine range of infusion rates. Such pumps are not capable of rapid intravenous infusion. Although some prior art infusion systems can deliver rapid infusion, those prior art rapid infusion devices are physically large, complex systems that require dedicated operation by skilled technicians.
Accordingly, what is needed is a device for rapid infusion that is compact and easily operated by conventional medical personnel in the course of their other duties. What is also needed is a low to high speed infusion device that utilizes a sterile, disposable fluid containment system that can be readily attached and removed from a separate pump system.
The rapid infusion system described herein is an adjustable mechanical pumping system for the intravenous delivery of fluids such as, but not limited to, blood, blood products, physiologic fluids, and medications. The present invention has several novel features that distinguish the rapid infusion system from the prior art. The present invention is much safer than prior art devices in that the present invention includes a self-leveling drip chamber that decreases the possibility of air entering the system thereby protecting the patient from air embolism. In addition, the self-leveling drip chamber adds to the efficiency and ease of use because the operator will not have to shut the system down to purge air from the lines.
Another advantage of the present invention is an integrated motor drive that allows the device to deliver a wide range of flow rates of fluids from a unit that is small and compact. In addition, the present invention provides a wide variety of flow rates with no change in the configuration of the drive system. Another advantage of the present invention is the pump chamber and drip chamber are in one disposable unit that is easily installed by the operator of the device. All of these unique features provide a rapid infusion system that is (1) small, light-weight and relatively inexpensive because of the simple design of the device; (2) flexible because the device can deliver wide ranges of flow rates of fluids without the need to change the configuration of the drive system; (3) safe because the possibility of air entering the delivery tubing is virtually eliminated; and (4) easy to use because the pump chamber and the drip chamber are in one, easily installed unit. The present invention is capable of rapidly delivering fluids with greatly reduced operational demands to a patient suffering from acute hypovolemia. The rapid infusion system offers improved mechanical functions and desirable operational improvements over previously known systems and practices in the management of critical, life-threatening situations.
In one preferred embodiment, the rapid infusion system includes a pump assembly, a drive assembly to power the pump, and a fluid containment system that keeps the infused fluid out of direct contact with the pump assembly and that is preferably disposable and removable. The system optionally includes components such as a pressure sensor and controller, a temperature sensor and controller, a filter to remove any occlusive material from the fluid, an automatic self-leveling system to keep the fluid in the drip chamber at an appropriate level for maximal delivery efficiency, and a sensor system to detect the presence of air bubbles in the fluid in conjunction with a switch that can stop the flow in the conduit in response to a detected air bubble of a dangerous size.
The flow rate of the pump advantageously is continuously adjustable and, preferably, can provide fluid flow rates from less than 20 cc/hour to more than 1,500 cc/minute. In a preferred embodiment, the pump is a roller pump and is connected with a drive assembly using a differential assembly to provide seamless transition from standard flow rates to high flow rates.
The present system provides a cost effective, yet safe method of handling sterile infusions, as all components of the system that physically contact the infused fluid are contained within or attached to a sterile, disposable cartridge designed for single use. In one embodiment, the single use pump cartridge includes a section of pre-formed tubing serving as the pump chamber. The cartridge includes a drip chamber that is self-leveling. Optionally, the system may include a temperature sensor at the output of the temperature controller for measuring and adjusting the fluid temperature to maintain the temperature within acceptable limits. Other embodiments of the system may also incorporate other monitoring sensors and feedback devices to allow adjustments to be made by the infusion system in response to physiologic measurements, such as central venous pressure, pulmonary arterial wedge pressure, urine output, pulse, mean arterial blood pressure, and similar parameters. Still other embodiments of the system may incorporate other monitoring sensors and feedback devices to allow either quantitative or qualitative adjustments in the infusium in response to in vivo sensors measuring parameters such as arterial pH, serum potassium, serum glucose, and other physiologic or chemical factors. The system also preferably includes a user display, which displays parameters including fluid temperature, line pressure, fluid flow rate, and total volume of fluid infused.
A further advantage of this system is that it does not require dedicated technical personnel for its operation, and it can readily be programmed and operated by nursing or emergency personnel in the course of their other patient care duties. Yet another advantage of this system is an electronic control system that allows precise, in vivo monitoring of blood pressure and/or chemistries, and the system may be programmed to make precise and automatic adjustments of the infusion rate to the patient based upon the monitored parameters.
An object of the present invention is to provide an adjustable system that is capable of standard to high volume infusion of fluids into a patient requiring such treatment.
A further object of the present invention is to provide a single-use, disposable fluid containment system for an infusion system that interfaces with permanent pump and control systems to provide safe, sterile, and contamination-free delivery of fluids to a patient.
Another object of the invention is to provide a pump cartridge for an infusion system that is fluid self-leveling.
Still another object of the invention is to provide a rapid infusion system that can deliver fluid at normal and rapid rates, and that can smoothly transition between normal and rapid infusion rates. In one embodiment, this smooth transition is achieved using a differential driver assembly that interacts with more than one motor and drives the pump.